1. Field of the Invention
The present invention relates to telecommunications systems and, particularly, to an improved system and method for multimedia conferencing.
2. Description of the Related Art
The ITU-T (International Telecommunications Union Telecommunications Sector) Recommendation H.323 defines a set of protocols for communicating using audio, video and data over packetswitched networks, such as for communication in telephony-over-local area network (ToL) systems. To accommodate multipoint conferences (i.e., those involving three or more parties), the Recommendation H.323 defines a multipoint control unit (MCU) to coordinate the conferencing. In particular, the MCU is required by the Recommendation H.323 to include a multipoint controller (MC), which handles H.245 signaling. In addition, the MCU may include one or more multipoint processors (MP), which mix and process the data streams. The MPs may also provide conversion, or transcoding, between different codecs.
In a centralized multipoint conference mode, the MCU handles call signaling, mixes audio and video streams, performs transcoding, and re-transmits the results to all parties to the conference. In a decentralized multipoint conference mode, the MCU does not process the media streams, which are instead handled directly between the endpoints.
Once a conference call is established, there is no way in conventional H.323 systems to change from a centralized to decentralized mode, or vice versa, as parties are added. Further, there is no way to switch from one MCU to another. That is, there is no way to change the site of the mixing of the media streams. Moreover, there is no way for an administrator to select a preference in choosing the site of the mixing of the media streams. Thus, as parties are added sequentially to a conference, sub-optimal mixing locations may be used.
This is illustrated by way of example in FIGS. 1A and 1B. As seen in FIG. 1A, an endpoint User A calls an endpoint User B. The endpoint User A then conferences in User C. Because the endpoint User A has sufficient resources, the endpoint User A handles the media mixing for the conference (i.e., the de-centralized model), as represented by paths A-B and A-C. Call signaling is handled with the MCU, in a known manner.
The endpoint User B may then wish to add an endpoint User D to the conference. However, if the endpoint User B does not have on-board mixing resources, a request will be made to the MCU to handle the mixing. The result is seen in FIG. 1B. The connections are now endpoint User A to MCU (A-MCU), endpoint User A to endpoint User C (A-C), endpoint User B to MCU (B-MCU), and endpoint User D to MCU (D-MCU). In effect, two conferences are occurring: When endpoint User A mixes media streams of MCU and endpoint User C, the MCU input is actually the result of the endpoint User B and endpoint User D media mix. When the MCU mixes media streams of endpoints A, B and D, the endpoint User A media input to the MCU is already the result of the endpoints A and C media mix.
As more calls are added, additional mixing locations may be necessary. If the ToL system spans a WAN (wide area network) or uses a gateway to connect to another system, long distance charges may be incurred as a result of poor mixing choices.
In such situations as well as other situations, it can be desirable to select a preference between long distance network cost or processor resource use in ToL multipoint conferencing.
These and other drawbacks in the prior art are overcome in large part by a telecommunications system in accordance with an embodiment of the invention. A telecommunications network includes a multipoint control unit coordinator (MCUC). The MCUC tracks all conferences in the system and determines how they can be best configured and modified over time. The MCUC instructs MCUs to break down and reconfigure calls, if necessary.
A MCUC according to an embodiment of the invention maintains a database of all the MCUs in the system, a measure of processing coding resources, and a geographical location. When two parties seek to add a third in a conference call, the MCUC determines coding resources, geographical locations, and determines the most appropriate mixing location based on such preferences. The MCUC then instructs the MCUs to handle the conference accordingly.